Paper1 Physical Geography, Section A: Hazards Knowlege Organiser Flashcards
(38 cards)
Hazard
An extreme event that threatens people, their property and settlements
Disaster
A hazard becomes a disaster when the hazard causes widespread destruction to property and human lives i.e. deaths
How hazardous or disastrous an event is also depends on:
Risk-the probability of an event happening and the scale of its possible damage
-the ability of a population to take preventative or precautionary measures, known as adjustment or mitigation, and their ability to cope
-how easy the hazard events are to predict
-the frequency of events
-that some places might have more than one type of hazard (multiple hazard zones e.g. Philippines or California)
-the severity of the hazard
What are the 2 types of Hazard categorisation?
-geological (e.g. volcanic eruptions, earthquakes)
-climatic (e.g. tropical storms)
-biological
-technical
Structure of the earth, crust:
- 0-70 km thick
- continental and oceanic crust
- solid->granite and basalt
- 10 degrees Celsius
Structure of the earth, mantle:
-2900km thick
-solid, but flows (rheological consistency)
-375 degrees Celsius
Structure of the earth, outer core:
-2000km thick
-liquid
-3000 degrees Celsius
Structure of the earth, inner core:
-1270km thick
-solid->iron and nickel
Oceanic crust?
-newer (less than 200 million years old)
-denser (heavier
-thinner -> 5km
-can subduct
Continental crust?
-older (1500 million years old)
-less dense
-thick -> 30km
-can’t subduct
Lithosphere
Top 100km of the earth (i.e. crust and top part of the mantle) that makes up the earth’s tectonic plates
Asthenosphere
The rest of the upper part of the mantle that acts as a lubricant for the tectonic plates to move on
How do tectonic plates move?
-slab pull
-ridge push
-convection currents
Constructive plate boundaries
-2 oceanic plates move apart
-creates effusive volcanoes and small volcanoes
-e.g. mid Atlantic ridge
Destructive plate boundaries
-oceanic plate sub-ducts under continental plate
-creates powerful earthquakes and explosive volcanoes
-e.g. Nazca plate sub ducting under South American plate
Collision
-2 continental plates collide
-causes powerful earthquakes and fold mountains
-e.g. Indian plate colliding with Eurasian plate
Conservative plate boundary
-2 continental plates slide past each other
-creates powerful earthquakes
-e.g.pacific plate and North American plate
Constructive boundary volcano formation
-two plates move away from each other
-magma rises to the surface at this weak spot and is extruded in eruptions, forming volcanoes when it solidifies to lava
- leads to shield volcanoes (shirt gently sloping volcanoes composed of basaltic lava due to low viscosity i.e. very runny) which have effusive eruptions
Destructive boundary volcano formation oceanic plate
-oceanic plate sub-ducts underneath continental plate
-oceanic plate melts due to dehydration melting
-newly created magma rises to the surface and is erupted
-forming a volcano over time as more material is erupted, cools, and solidifies to lava
-forms strata volcanoes
Shield volcanoes
-shield volcanoes (shirt gently sloping volcanoes composed of basaltic lava due to low viscosity i.e. very runny) which have effusive eruptions
Strato volcanoes
- tall, steep sided volcanoes
-composed of alternating layers of lava and pyroclastic flow/ash deposits due to sticky, high viscosity rhyolitic lava
-have explosive eruptions
Hotspot volcanoes
-where isolated plumes of magma rise and move up through the crust to create a chain of volcanoes e.g. Hawaii
Worldwide distribution of volcanoes
-uneven distribution
-mostly correlate with plate boundaries
-earthquakes occur in linear chains (e.g. along the west coast of South America) along all types of plate boundary
-some earthquakes away from plate boundaries (could be due to large plate movement or due to human activity such as building dams and reservoirs
Primary hazards
Immediate effects, resulting from the eruption e.g. lava flow, ash, pyroclastic flow etc.
